Laser ablation-inductively coupled plasma-mass spectrometric analysis of fluid inclusions from the Windy Craggy Cu-Co-Au volcanogenic massive sulphide deposit: method development and preliminary results

Abstract

There is increasing recognition that there is a variable magmatic component to mineralizing fluids in volcanogenic massive sulphide (VMS) deposit formation. A previous fluid inclusion study conducted on the Windy Craggy Cu-Co-Au deposit in northwestern British Columbia documented primary inclusion fluids salinities that are higher than typical VMS fluids. The previous study concluded that the high salinity indicates a magmatic contribution to the ore-forming system. This makes Windy Craggy an ideal study location to test if there is in fact a magmatic influence on the fluids and to quantify that contribution. Preliminary results of this study show fluids consistent in salinity and temperature with those observed in the previous study. Fluids with salinities between 6.2 and 12.2 weight % NaCl equivalent are documented. Laser ablation ICP-MS analysis of these inclusions detects Na, K, Ca, Cu, Sr, Sn, Sb, Ba and Pb as well as trace elements of potential magmatic origin, including Au, W, Sn, In and Bi. Due to the multiple possible sources of Sn, we will be focusing on other potential magmatic elements such as Au, Bi and In as the study progresses. The small number of samples analyzed to date precludes us from making definitive conclusions. However, the detection of some potential magmatic elements in 17 inclusions is promising.